Musculoskeletal System: Head

The neck is considered to be quadrangular. This shape is the basis to study various components of the neck and their relations. The boundaries of the quadrangular shape include the mandible, upper border of the clavicle, midline of the neck, and anterior margin of the trapezius. The quadrangular shape is divided into an anterior and posterior triangle by the sternocleidomastoid muscle (SCM). The anterior and posterior triangles are the 2 primary subdivisions and are delineated by easily recognized anatomic structures. Each triangle houses muscles, nerves, vasculature, lymphatics, and adipose tissue.

The facial muscles (also called mimetic muscles) control facial expression and are supplied by the facial nerve. Most of them originate from the skull and attach to the skin around the facial openings, which serve as a method to group or classify them. Also located within the face are the masticatory muscles, which move the temporomandibular joint, allowing for mastication and the initial stages of digestion.

The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. The neurocranium is further subdivided into the calvarium (the skullcap) and the base of the skull (the cranial fossa).

Normally, an adult has 32 teeth: 16 maxillary and 16 mandibular. These teeth are divided into 4 quadrants with 8 teeth each. Each quadrant consists of 2 incisors (dentes incisivi), 1 canine (dens caninus), 2 premolars (dentes premolares), and 3 molars (dentes molares). Teeth are located within the alveolar processes and are held in position by the periodontal ligament. Teeth are composed of enamel, dentin, and dental cement.